.TH PUMP 1
.SH NAME
pump \- copy asynchronously via a large circular buffer
.SH SYNOPSIS
.B pump
[
.B -b
.I iando
] [
.B -d
.I sleepms
] [
.B -f
.I ofile
] [
.B -i
.I ireadsize
] [
.B -k
.I KB-buf
] [
.B -o
.I owritesize
] [
.B -s
.I start-KB
] [
.B -S
.I off
] [
.B -t
.I minutes
] [
.I file
\&... ]
.SH DESCRIPTION
.I Pump
copies
.IR files
(or standard input if none)
to standard output
by using two processes,
one reading and one writing,
sharing a large circular buffer,
thus permitting the reading process to
get ahead of the writing process if the
output device is slow (e.g., an optical disc).
This in turn can keep the output device busy.
The pipeline
.L "dd | dd"
can approximate this, but pipe buffering is limited to 64K
bytes, which is fairly modest.
.PP
Options are:
.TF \fL-m
.TP
.B -b
sets the size of
.I read
and
.I write
operations to
.I iando
bytes.
The default size is 8 kilobytes.
.TP
.B -d
causes the output process to sleep for
.I sleepms
milliseconds initially, giving the reading
process time to accumulate data in the buffer.
.TP
.B -f
writes
.I ofile
rather than standard output
.TP
.B -i
sets the size of
.I read
operations to
.I ireadsize
bytes.
.TP
.B -k
allocates a circular buffer of
.I KB-buf
kilobytes rather than the default
5000 kilobytes.
.TP
.B -o
sets the size of
.I write
operations to
.I owritesize
bytes.
.TP
.B -s
prevents output until
.I start-KB
kilobytes have been read.
.TP
.B -S
seeks both input and output files to
.I off
before copying.
.TP
.B -t
stops output after
.I minutes
have passed.
This assumes that
.I pump
can copy 10,584,000 bytes per minute.
.SH EXAMPLES
Append a
.IR venti (8)
arena to a DVD or BD quickly.
.PD 0
.IP
.EX
cdfs
venti/rdarena arena0 arena.3 |
	pump -b 65536 -k 51200 >/mnt/cd/wd/arena.3
.EE
.PD
.\" .SH FILES
.SH SOURCE
.B /sys/src/cmd/pump.c
.SH SEE ALSO
.IR cp (1),
.IR dd (1),
.IR ecp (1),
.IR cdfs (4)
.SH BUGS
.I Pump
processes spin while waiting for the circular buffer
to fill or drain.
.PP
.IR Dd ,
.IR ecp
and
.I pump
occupy slightly different niches
but perhaps some simplification is possible.